Things generally go more smoothly with a lawyer, but you may be able to negotiate the diversion program on your own. That would be the best possible outcome for your case as it is the only way you can get expungement so that future employers and colleges won't find out about this arrest.
Some courts have information about their Pre Trial Diversion Programs online. You sound like an ideal candidate for such a program. Apply for a public defender and ask them to explain in detail what is needed. In general, you will need to pay a program fee, do some community service, stay out of trouble for a period of time, and attend counseling or classes. Some jurisdictions in Georgia also require people in your age range to write an essay.